Foot arch is part of a human foot structure providing shock absorption in walking or exercising to reduce the risk of foot injuries. Generally, a foot arch type can be determined by the height of the foot arch, which refers to the distance from the medial longitudinal foot arch to the ground. Typically, the perpendicular distance from the lower rim of the navicular tuberosity to the ground is used as an index; a high arched foot and low arched foot if the distance is too large or too small. If the distance is smaller to a certain level, the foot is referred to as a flat foot. In recent years, studies have shown a close relationship between abnormal arch height (high or low arch) and sport related injury to lower limbs.
Foot arch type can be evaluated by a variety of ways, such as medical instruments (X-ray examination, ultrasound examination), measuring instruments (caliper measurement, foot type measurement), footprint observation and experimentation (footprint parameters, wet foot test). Due to its easy, convenient and non-invasive characteristics, the footprint is more commonly used for measurement of the height of foot arch. In footprint analysis, geometrical methods such as calculation of line segment lengths, angles and areas are widely used for estimation, and commonly utilized footprint parameters include the arch angle, the footprint index, the arch index (AI), the arch length index and the truncated arch index. The most commonly used arch index (AI) is disclosed by Cavanagh and Rodgers in 1985. It is calculated by obtaining a footprint under a static standing stance, and dividing the length L of the footprint area without toes equally into three sections (referring to FIG. 1), and then obtaining the areas of the three sections, including the rear foot area (A), the mid foot area (B) and the forefoot area (C). The arch index (AI) is calculated by dividing the mid foot area to the total foot area (without the toes), which means AI=B/(A+B+C). When the arch index AI is smaller than 0.21, the foot arch type is high arch. When the arch index AI is between 0.21 and 0.26, the foot arch type is normal arch. When the arch index AI is larger than 0.26, the foot arch type is flat foot.
However, calculation of the footprint parameters requires complex steps and huge calculation cost (such as footprint area integral). Thus, the identification of foot arch type is generally not complete in a short time and cannot provide suitable insoles or shoes for the consumer.
Therefore, in view of the aforementioned technical problems, there is a need for a method of measuring and identifying foot arch type to solve the aforementioned problems.